Absorption and metabolism of capsaicinoids following intragastric administration in rats.
This study was performed to examine the metabolism and absorption of intragastrically administered capsaicinoids in the anaesthetized rat. [3H]-dihydrocapsaicin ([3H]-DHC) and unlabelled capsaicin were readily absorbed from the gastrointestinal tract but were almost completely metabolized before reaching the general circulation. A certain degree of biotransformation already took place in the intestinal lumen. Unchanged compounds (identified by chromatography) were present in portal vein blood. There seems to be a saturable absorption and degradation process in the gastrointestinal tract and a very effective metabolism in the liver. Less than 5% of the total amount of extracted radio-activity consisted of unchanged [3H]-DHC in trunk blood and brain 15 min after gastrointestinal application. On the other hand, approximately 50% unchanged [3H]-DHC was detected in these tissues 3 min after i.v. or 90 min after s.c. application of the capsaicinoids. Dihydrocapsaicin (DHC) or [3H]-DHC were metabolized when incubated in vitro with liver tissue but not with brain tissue. The metabolic product(s) did not show capsaicin-like biological activity. It can be concluded that rapid hepatic metabolization limits systemic pharmacological effects of enterally absorbed capsaicin.
Donnerer
J
J
Institut für Experimentelle und Klinische Pharmakologie, Universität Graz, Austria.
Amann
R
R
Schuligoi
R
R
Lembeck
F
F
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D007408:Intestinal Absorption; D007441:Intubation, Gastrointestinal; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D002211:Capsaicin; C012906:dihydrocapsaicin